Frontier molecular orbital theory has proved to be an immensely useful concept. The concept of HOMO-LUMO interactions are frequently employed in detailing the mechanistic descriptions of reactions in organic chemistry. It seems to me that there are numerous examples of HOMO-LUMO interactions seem to be responsible for kinetic phenomena.
For example, secondary orbital interactions allow the preference for the endo product in the Diels-Alder reaction under kinetic control.
Nucleophilicity, which is often linked to the energy of the HOMO of the nucleophile, is also often regarded as a kinetic phenomenon. In fact, Lewis basicity itself may even be seen as a kinetic concept. For example, we make the assertion that phosphine is a better nucleophile (and also better Lewis base) compared to ammonia because $\ce {P}$ is less electronegative than $\ce {N}$ and thus, the HOMO of $\ce {PH3}$ is thus higher in energy, compared to that of $\ce {NH3}$.
Should we thus classify frontier orbital interactions as a kinetic concept?
